Resonant Photoemission Studies of Thickness Dependence of the Unoccupied Gd 5d Bands

Authors

Peter A. Dowben, University of Nebraska-LincolnFollow
Dongqi Li, Argonne National Laboratory, Argonne, IL
Jiandi Zhang, University of Nebraska-LincolnFollow
M. Onellion, University of Wisconsin, Madison

Date of this Version

10-24-1994

Comments

41st American Vacuum Society National Symposium, Denver, CO, October 24- 28, 1994, to be published in Jour. Vacuum Science and Technology.

Abstract

Ultrathin Gd films have been studied with constant initial-state spectroscopy (CIS) of photoemission utilizing linearly polarized light of synchrotron radiation. The photoemission cross-section of the 5d surface state near EF shows strong photon energy dependence, i.e., sharp peaks in CIS spectra near the Gd 5p_1/2 adsorption edge. These peaks originate from resonant photoemission processes involving the occupied 5p and unoccupied 5d levels of the surface atoms. The symmetry of the unoccupied states were determined experimentally by changing the polarization of light, where p-polarized light excites only to the unoccupied d_z² or d_xz,yz states and s-polarized light to all the d states. including d_x²-y² and d_xy states. Based on the symmetry assignments, the lower bound of the exchange splitting of the Gd 5d_z² surface state can be abstracted, which increases when the thickness of Gd film decreases and reach maximum at the monolayer limit.